Coated die structure and method



Feb. 17, 1959 M. J. CELOV SKY 2,

COATED DIE STRUCTURE AND METHOD Filed June 24, 1953 2 Sheets-Sheet 1.IZYZE YZZET MC'HA'EL cf CEL 01/55,

Feb. 17, 1959 M. J. CELOVSKY COATED DIE STRUCTURE AND METHOD Filed June24. 1953 2 Sheets-Sheet 2 Maw/25L (I CELOl/SEV United States Patent '0COATED DIE STRUCTURE AND METHOD Application June 24, 1953, Serial No.363,856

2 Claims. (Cl. 113-49) The present invention relates to improvements insheet metal drawing or forming die techniques, and more particularlyrelates to the provision of a die member against which highly polishedsheet metal surfaces can be pressed without damage to the finish of thesheet metal article.

An important object of the present invention relates to the treatment ofshaping or forming die surfaces for sheet metal work to enable highlypolished sheet metal surfaces to be pressed under substantial pressureagainst the die surfaces without abrading or otherwise damaging thepolished surfaces.

A further object of the invention is to provide an improved coated diestructure.

Still another object of the invention is to provide a sheet metal diestructure having the surface thereof treated to provide a thincushioning layer thereon which will withstand high pressures in servicewithout damage.

Yet another object of the invention is to provide a novel coating forthe pressure surfaces of sheet metal dies.

Other objects, features and advantages of the present invention will bereadily apparent from the following detailed description of certainpreferred embodiments thereof, taken in conjunction with theaccompanying drawings in which: I

Figure 1 is a more or less schematic vertical sectional detail view of aportion of a sheet metal working die of a kind particularly adapted formaking wheel covers, and embodying features of the present invention;

Figure 2 is a fragmentary top plan View of a coated die member of theassembly shown in Figure 1;

Figure 3 is a fragmentary more or less schematic vertical sectional Viewthrough a modified form of sheet metal working die assembly embodyingfeatures of the invention;

Figure 4 is a fragmentary top plan view of a coated die member of theassembly of Figure 3; and

Figure 5 is a fragmentary side elevationalview of a wheel cover after ithas been formed in the die assembly of Figure 3.

In the manufacture of sheet metal articles such as wheels covers, thatis covers adapted to be applied to the outer sides of vehicle wheelssuch as automobiles, certain forming operations must be performed afterat least certain external surface areas of the cover have been highlypolished. As an incident to the forming operations, the highly polishedsurface areas are necessarily forced with substantial pressure against adie surface and are therefore liable to abrasion or pressure damage ofthe polished areas.

According to the present invention, the surfaces of the die elementswhich must engage under pressure with highly polished surface areas ofsheet metal articles such as wheel covers in the process of formation ofthe articles are coated with a highly pressure resistant, .chipproofthin cushioning coating of an enamel, and more particularly a syntheticenamel. Excellent results have been obtained in practice with an enamelin which the 2,873,709 Patented Feb. 17, 1959 body ingredient is aphthalic alkyd resin. In a preferred formula, the enamel comprisespigment approximately 20.8%, synthetic resin 30.2%, solvents 49% andcomprising aliphatic hydrocarbon 18.1% and aromatic hydrocarbon 30.9%.For ready identification of the surface the pigment is preferably abright color such as chrome yellow.

In treating a die surface with the enamel, the die surface is firstcleaned in hot caustic solution and is thereafter bonderized, that is,treating the surface with a solution of primary manganese di-hydrogenphosphate and a small percentage of a copper salt by dipping or sprayingon the solution. Thereafter, the enamel is sprayed onto the die surfaceto be treated in a double wet coat. The coated surface is then baked at280 to 290 F. for about one hour. No driers are used in the enamel. Thealkyd resin is preferably in a pure, unmodified form. The resultingcoating is highly resistant to pressures, is satisfactorily resilientand is chipproof. It is thus long wearing so that a die can be used alarge number of times without requiring recoating.

As an example of a die structure in which the present invention hasfound-a high degree of utility, reference is made to Figures 1 and 2. Adie base 10 has thereon circular ring dies comprising an inner diemember 11 and an outer die member 12 which are provided with workingsurfaces properly profiled to match and thereby receive uniformlythereagainst the outer surfaces of a wheel cover plate 13 made fromsheet metal and having the outer surfaces thereof highly polished as toa substantially mirror finish. In the present instance, the inner diering 11 serves primarily as a centering die to receive a more or lessfrusto-conical intermediate portion 14 of the cover plate 13, while theouter die member 12 provides a. bearing surface to receive uniformlythereagainst an outer marginal portion 15 of the cover plate and tosupport such outer marginal portion against deformation while a holddown ring die member 17 presses an outer marginal portion of a secondcover plate member 18 against the back face of the cover plate portion15. As will be observed, the cover plate 18 has a portion 19 thereofdirected convergently to the outer extremity portion of the cover margin15 where a marginal extremity flange 20 of the cover portion 19,

ably by a die head 21, with springs 22 normally urging the hold down diering 17 into substantial spaced relation to a backing plate member 23carried by the die head 21.

Upon downward movement of the die head 21 to drive the hold down ring 17against the marginal portion 20, a crimping die ring 24 carried by theouter perimeter of the backing plate 23 operates to turn an extremityflange 25 of the marginal portion 15 over into crimped retainingrelation to the plate margin 20 for thereby uniting the cover plates 14and 18. Pressure of the hold down member 17 is reflected in substantialpressure of the cover marginal portion 15 against the opposing bearingsurface of the die member 12. Accordingly, the bearing surface of thedie member 12 is provided with a cushioning coating 27 of the protectivecoating enamel as described hereinabove. This affords protection againstdamage of the highly polished external surface of the cover marginalportion 15.

Inasmuch as direct pressure from the hold down member 17 is exerted on anarrow annular marginal extremity portion of the cover portion 15, ithas been found desirable to omit the cushion coating 27 from the annularouter extremity marginal area of the hearing surface of the die ring 12,as indicated at 28. The

concentration of pressure in this narrow area is so great that the lifeof the enamel coating would be too short to be practicable in thisnarrow area as compared to the remainder of the bearing area. Moreover,the narrow area 28 is preferably highly polished complementary to thehighly polished surface of the opposing cover surface so that danger ofdamage of the highly polished surface is substantially eliminated.

In the modified die assembly of Figures 3 and 4, a cover of differenttype is shaped. In this die assembly, a base plate 30 supports a ringdie member 31 carrying a clamping ring die member 32 which is normallyelevated relative to the die member 31 through the medium of springs 33.

Opposing the clamping ring 32 is a hold down ring die member 34 attachedto a forming die ring 35 carried by a backing plate 37 supported by adie head 38. The die ring 35 has forming surfaces 39 cooperative withrecesses 40 in the underlying die ring member 31 inside of the clampingdie ring 32 for producing embossments 41 in a cover member 42 which hasa marginal annular portion 43 of dished cross-section clamped betweenthe clamping ring 32 and the hold down die member 34 during the formingor drawing action of the cooperative die members.

Since the outer dished surface of the cover portion 43 is highlypolished and bufied to a mirror finish, it must be protected againstpressure damage between the die members 32 and 34. To this end, thecover surface opposing bearing surface of the clamping die member 32 isprovided with a protective enamel coating 44. This provides a cushionand protective resilient surface between the bearing face of the diemember 32 and the highly polished surface of the cover portion 43. Itwill be observed that inasmuch as the pressure against the cover portion43 is substantially uniformly applied over the entire surface engagingthe clamping die member 32, the entire bearing surface is coated withthe coating 44.

It will be understood that modifications and variations may be effectedwithout departing from the scope of the novel concepts of the presentinvention.

I claim as my invention:

1. In a die structure, a circular die member having an annular surfacereceptive of a highly polished complementary surface of a sheet metalmember and against which annular die surface the sheet metal member mustbe pressed with substantial pressure for holding the sheet metal memberimmovable while forming operation is effected upon the sheet metalmember by yet other die means, said annular surface having thereon,except for a narrow annular marginal portion thereof, and thoroughlybonded thereto a highly pressure resistant but satisfactorily resilientand chip-proof layer of a sub- 5 stantrally pure unmodified alkyd resinenamel free from driers and fused by baking, and effective as a cushionto prevent abrasion or pressure damage of the polished sheet metalarticle surface pressed thereagainst, said narrow marginal portion beinghighly polished for receiving thereagainst a corresponding narrowannular portion of the surface of the sheet metal member against whichforming pressure is applied in excess of the pressure applied againstthat portion of the sheet metal surface opposed by the bakedenamel'cushion.

2. In a process for die shaping sheet metal articles having polishedsurfaces susceptible of marring when subjected to forming pressurebetween opposing dies and which polished surfaces must be protectedagainst marring while being subjected to the forming pressures betweenthe dies, the method of preparing a die member for supporting against asubstantial surface area thereof an opposing highly polished surface ofa sheet metal member under substantial pressure of the opposing diedirected toward said die member surface area, cleaning said surface areaof the die member, treating said cleaned surface area to enhance theadhesion thereto of an enamel coating, applying to said die surface areain fluid form an enamel composition free from driers and consistingessentially of a substantially pure unmodified phthalic alkyd resin asthe major solids component, and solvents, and baking the coating for atime interval and at a temperature sufficient completely to fuse theenamel coating and provide a highly compression pressure resistant andchip-proof resilient cushion upon said die surface area, serving as aprotection against marring of the polished sheet metal surface pressedthereagainst and then pressing the polished surface of said metal memberagainst the resilient cushion protected surface area of said die member.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Publication: Alkyd Resins as Film-Forming Materials, GeneralElectric Co. (-1929).

Publication: Heat Treating and Forging magazine, June 1943, pages290-291.

